A hyper-redundant manipulator

“Hyper-redundant” manipulators have a very large number of actuatable degrees of freedom. The benefits of hyper-redundant robots include the ability to avoid obstacles, increased robustness with respect to mechanical failure, and the ability to perform new forms of robot locomotion and grasping. The authors examine hyper-redundant manipulator design criteria and the physical implementation of one particular design: a variable geometry truss

Discrete Cosserat Approach for Multi-Section Soft Robots Dynamics

In spite of recent progress, soft robotics still suffers from a lack of unified modeling framework. Nowadays, the most adopted model for the design and control of soft robots is the piece-wise constant curvature model, with its consolidated benefits and drawbacks. In this work, an alternative model for multisection soft robots dynamics is presented based on a discrete Cosserat approach, which, not only takes into account shear and torsional deformations, essentials to cope with out-of-plane external loads, but also inherits the geometrical and mechanical properties of the continuous Cosserat model, making it the natural soft robotics counterpart of the traditional rigid robotics dynamics model. The soundness of the model is demonstrated through extensive simulation and experimental results for both plane and out-of-plane motions.Comment: 13 pages, 9 figure

Improving Strength and Stability in Continuum Robots

Continuum robots, which are bio-inspired ’trunk-like’ robots, are characterized for their inherent compliance and range of motion. One of the key challenges in continuum robotics research is developing robots with sufficient strength and stability without adding additional weight or complexity to the design. The research conducted in this dissertation encompasses design and modeling strategies that address these challenges in strength and stability. This work improves three continuum robot actuation paradigms: (1) tendon-driven continuum robots (TDCR), (2) concentric tube robots (CTR), and (3) concentric push-pull robots (CPPR). The first chapter of contribution covers strategies for improving strength in TDCRs. The payload capacity and torsional stiffness of the robot can be improved by leveraging the geometry of the backbone design and tendon routing, with design choices experimentally validated on a robot prototype. The second chapter covers a new bending actuator, concentric precurved bellows (CPB), that are based upon CTR actuation. The high torsional stiffness of bellows geometry virtually eliminates the torsional compliance instability found in CTRs. Two bellows designs are developed for 3D printing and the mechanical properties of these designs are characterized through experiments on prototypes and in static finite element analysis. A torsionally rigid kinematic model is derived and validated on 3D printed prototypes. The third chapter of contribution covers the development and validation of a mechanics-based CPPR kinematics model. CPPRs are constructed from concentrically nested, asymmetrically patterned tubes that are fixed together at their distal tips. Relative translations between the tubes induces bending shapes from the robot. The model expands the possible design space of CPPRs by enabling the modeling of external loads, non-planar bending shapes, and CPPRs with more than two tubes. The model is validated on prototypes in loaded and unloaded experiments

Continuum robot actuation by a single motor per antagonistic tendon pair: Workspace and repeatability analysis [Kontinuumsroboter-Aktuierung mittels eines Motors pro antagonistischen Kabelpaar. Arbeitsraum- und Wiederholgenauigkeitsanalyse]

Kontinuumroboter sind stark im Fokus aktueller medizinrobotischer Forschung. Da die meisten der in der Literatur vorgestellten Systeme jedoch komplexe und große Aktoreinheiten aufweisen, kann das Erstellen eines solchen Systems in aufwendigen, kostenintensiven und sperrigen Aufbauten resultieren, welche ungeeignet für die räumlichen Anforderungen des Einsatzes in medizinischen Szenarien sind. In dieser Arbeit wird ein einfaches, effizientes kontinuumrobotisches System vorgestellt, in welchem ein antagonistisches Paar von Kabelzügen durch einen Servomotor bewegt wird, anstatt jedes Kabel durch einen einzelnen Motor zu treiben. Auf diese Weise kann die Grundfläche der Aktoreinheit klein gehalten werden und die Methode resultiert in einem einfacheren Aufbau. Der resultierende 260 mm lange Roboter mit 9,9 mm Durchmesser erreicht eine Wiederholgenauigkeit von 1,8 % seiner Länge. In zukünftigen Arbeiten dient er als Basis für die Integration von verschiedener Sensormodalitäten in Kontinuumroboter und zur Evaluation von Steueralgorithmen

CABLE DECOUPLING AND CABLE-BASED STIFFENING OF CONTINUUM ROBOTS

Cable-driven continuum robots, which are robots with a continuously flexible backbone and no identifiable joints that are actuated by cables, have shown great potential for many applications in unstructured, uncertain environments. However, the standard design for a cable-driven continuum robot segment, which bends a continuous backbone along a circular arc, has many compliant modes of deformation which are uncontrolled, and which may result in buckling or other undesirable behaviors if not ameliorated. In this study, a detailed approach for using additional cables to selectively stiffen planar cable-driven robots without substantial coupling to the actuating cables is investigated. A mechanics-based model based on the planar Cosserat equations is used to find the design conditions under which additional cables can be routed without coupling of the cable lengths for small deformations. Simulations show that even for relatively large deformations, coupling remains small. A prototype was designed and evaluated, and it was demonstrated that the compliance of the robot is substantially modified relative to the same robot without the additional stiffening cables. The additional stiffening cables are shown to increase the end-effector output stiffness by a factor of approximately 10 over a typical design with actuating cables